It is known to make rovings for reinforcement of plastics and other materials by pulling fibers such as glass fibers from molten glass exiting tips of a fiberizing bushing, spraying a water mist on the fibers to cool the rapidly moving fibers followed by applying a conventional aqueous chemical sizing to the fibers, gathering the fibers into one or more strands and winding the strand(s) onto a rotating collet to form a wet roving package or cake. Roving packages are not finished products, but instead are tubular or cylindrical shapes of tightly wound wet glass fiber strands having square ends and a hollow cylindrical passage having the shape of the collet down the center of the package. Cakes are typically wound on a paper or plastic sleeve placed on the collet, the sleeve staying with the cake until the cake is dried. Cakes can be of different shapes, but typically are cylindrical with tapered end portions. When the wet fiber strands are wound on a shaped spool, bobbin, the bobbin stays with the fiber strands and are called bobbins of rovings strands of fiber or fiber, bobbins for short.
The wet roving package, cake or bobbin is then dried, usually in a gas fired or electric oven, to remove the water and to cure the binder in the sizing. Some typical processes for making such wound continuous fiber packages or cakes are disclosed in U.S. Pat. Nos. 4,546,880, 5,613,642 and pages 218-230, and elsewhere, of THE MANUFACTURING TECHNOLOGY OF CONTINUOUS GLASS FIBERS by K. L. Loewenstein, published by Elsevier (1983), the disclosures of which are herein incorporated by reference. This type of drying is very slow and also tends to cause the binder on the fibers to migrate to the surface resulting in a binder rich product in the outer layer of fiber strands on the roving package or cake, an undesirable result because much of this outer layer must be removed and discarded before shipping a roving product. It is known to reduce migration of the resin(s) in the sizing during drying by modifying the sizing composition as shown by U.S. Pat. No. 4,104,434, but this technique is frequently not usable with sizings aimed at achieving the optimum bonding with many polymers and properties in fiber reinforced composites.
Monorail systems are also known that move hangers through fiber forming rooms where the operators place wet roving packages and/or cakes on the hangers. The monorail system moves the cakes to either a staging area outside the forming rooms where the roving packages or cakes are transferred to either wheeled trucks or monorail type racks for holding a plurality of wet roving packages and/or cakes to be put into the drying chamber(s). Monorail systems are also known that run the wet cakes on hangers coming through the forming rooms directly into drying tunnel chambers to dry the wet roving packages and/or cakes using fuel/air burners or electrical resistance heating. It is also known to use dielectric drying to dry cakes and roving packages as disclosed in pages 228-229 of Loewenstein (see above cite), but total electrical drying is expensive, particularly where electrical costs are high.
It is also known to generate electricity using a gas turbine or other heat engine that exhausts gases at elevated temperatures and it is known to use these gases in a heat exchanger to preheat the air and/or gaseous fuel used to drive the gas turbine or heat engine.